This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-1492 filed Jan. 9, 2001.
The present invention relates to a power generation controller and method for a vehicle.
In a power generator for vehicles, it is proposed in JP-U-62-44698 to detect a start of a rotor in a power generator, which indicates a start of an engine, by utilizing small AC voltages appearing in a stator winding. Since the AC voltage generated only by a remaining magnetic flux in a field core of the rotor is very small, the small voltage cannot be detected when a DC leak current (shown with solid line in FIG. 5) flows from the higher potential side of an on-board battery to the power generator. It is difficult to detect the voltage until the rotation of the rotor becomes relatively high. It is also difficult to perform this voltage detection due to susceptibility of a contact resistance in the power generator to environmental disturbances.
In order to counter these problems caused by a leak current, detection circuits are proposed in U.S. Pat. No. 5,182,511 and No. 5,602,470 (JP-A-3-215200 and JP-A-8-503308). In these circuits, two phase voltages are detected. However, more connections between the stator winding and the detection circuit are required in these circuits, making the structure of the power generator complex and decreasing reliability.
The present invention therefore has an objective to provide a power generation controller and method for a vehicle that can maintain the accuracy of rotation detection even when a leak current occurs.
To attain this objective, a power generation controller for a vehicle controls an output voltage of the power generator by turning on and off a current supply a field winding of the power generator. The controller detects a start-up condition of power generation when the frequency of a phase voltage in the stator winding of the power generator exceeds a predetermined value. The controller temporarily connects a resistor in series between a terminal where the phase voltage is applied and a negative terminal of a battery, in response to the detection of start-up condition.
According to the present invention, even when the phase voltage increases due to occurrence of a leak current, the leak current is passed to the negative terminal of the battery via the resistor temporarily turned on. Therefore, the phase voltage with small amplitude will not be masked by DC drifting component. As a result, the accuracy of rotation detection can be maintained even when the leak current occurs.